Didn't notice it in the video, but in the screenshots it seems like skyrims visuals are getting slightly enhanced. See the ash spawn image.

From other areas in skyrim, such as the college, the distance view to vvarenfell is horrible. The edge of the view looks cut off. Hope this addon does something about that.

It's possible, adding content like this takes a toll on the game so their enhancing the core too.

I am sure they are going for a different look and feel, since it is a different province. Shivering Isles had a different look and feel than Oblivion, even though it looked like it belonged with that game. These differences can be done with subtle lighting and shadow effects.

Good point

But depth of field is a nice cinematic enhancement.

Could be some sort of special effect imagespace. That seems far too strong for a general DoF shader.

The depth of field is from the menu, on the pc you can use this by disabling the menu to make screens, but no use to normal gameplay.